Displacement around a test chamber in granite at Du Toitskloof

The proposed new Du Toitskloof road tunnel is planned to allow for two tunnels, each of two lanes, 36 metres apart and 3,9 km long. The tunnel route traverses mainly intact granite and TMS sandstone of the Klein Drakenstein mountains between Paarl and Worcester ( Figure 1 ). A major project of this scale requires reliable predictions of the nature and structure of the rock mass along the entire length of the tunnel for economy of design and construction. For this purpose, a pilot bore was constructed along the line of the proposed second main tunnel and various geotechnical investigations were conducted.